Gordon Brown will today recommend that civil partnership ceremonies should be allowed to be held in the Palace of Westminster as a symbol of parliament's commitment to gay marriage and tolerance.

He will make the recommendation when he gives evidence to the Speaker's conference, along with the Conservative and Liberal Democrats leaders, David Cameron and Nick Clegg. It had been expected that they would give evidence jointly, but the Tories said, as a result of pressure from Downing Street, the leaders would present their 20-minute evidence consecutively. The Speaker's conference is examining how to attract more minority groups and women into parliament, as part of a drive to make it more representative.

There are relatively loose rules on the venues for civil services. Stately homes, hotels, selected beaches and mountain tops can all be legitimate places to marry, as long as they are registered by the local council. Same-sex partners have been able to register a civil partnership since December 2005.

Many heterosexual political obsessives have chosen to get married in the Commons crypt, including William Hague, Charles Kennedy and more recently Michael Mates. Civil partnership ceremonies without religious content can be held in churches.

Brown, in his evidence session today, will also commit his party to trying to ensure there are 120 female Labour MPs in the parliamentary party after the next election, on the assumption that Labour maintains its current number of seats. Labour has 95 female MPs and claims that nearly two-thirds of its new parliamentary candidates are women. It says the number of female Labour MPs would rise to 120 is based on the continued use of all-women shortlists and an optimistic view of how the party is likely to fare at the election.

An interim report by the Speaker's conference published in the summer found the Commons does not reflect the fact that, in society at large, there are more women than men, approximately one in five people is disabled and 7.9% of the population come from black and minority ethnic backgrounds.

The proportion of the population which is lesbian, gay, bisexual and transgender is not monitored, but official estimates put the proportion at 6-9%.

If the Tories secure the 7% swing they need to have an overall majority, the Commons would continue to have 126 female MPs, it has been estimated by Madano, a communications consultancy. The Tories have 18 female MPs, but this would rise to 60 on the basis of theswing. Labour would fall from 95 to 58 female MPs.

But there are many imponderables. Labour has about 50 seats still to select candidates, with more MPs in safe seats expected to announce they are standing down. The Tories are in a similar position.